This invention relates to a test device for monitoring a predetermined pressure load on a patient""s foot as exerted by a body rate of the patient during walking.
Test devices of the above kind are used for warning a patient in those cases were due to a fracture of a leg or any other orthopedic surgery operations the factual load on the patient""s leg as related to the patient""s body weight must be limited. As regards the particular therapy of more or less complicated leg fractures as well as orthopedic operations for example on a patient""s hip an initial load on the patient""s foot of only about 20 kg is more generally considered as an allowable maximum limit when the patient will start with his first attempts to walk after a respective operation. Such a lowermost load which of course is only a fraction of the patient""s body weight will then subsequently be increased stepwise whereby only with a corresponding number of steps of increasingly higher pressure loads on the patient""s foot a correct heeling or recovery of the operated leg or hip will be secured. It is therefore most essential to continuously monitor the pressure load on the patient""s foot as exerted during walking by any suitable test device which should be easy in handling by the patient.
A prior art device as described in German Patent Publication DE 41 00 834 A1 comprises an elastic pressure chamber filled with air under atmospheric pressure and provided for being placed under the patient""s foot. The pressure chamber forms a pressure sensor which is incorporated into a shoe sole and interconnected with an analog indicating instrument via a flexible line whereby the indicating instrument comprises an electronic measurement equipment and indicator lamps for indicating a correct or otherwise incorrect pressure load on the patient""s foot.
A similar test device is described in U.S. Pat. No. 6,031,463 which comprises as a pressure sensor a resilient foot pad filled with a fluid and connected via a fluid line to a pressure responsive means that is adapted to actuate a signalling means at a predetermined pressure of the liquid in the resilient foot pad under a predetermined load on the patient""s foot. The signalling means comprises a so-called click spring which is arranged for supplying an audible click noises when actuated by the pressure responsive means, the click noise being obtained by a translent deformation of a deformable bulge of the click spring whenever the click spring is leaving a respective rest position and is again returning to the same. The click spring is preferably arranged within a box serving as a resonance body for amplifying its click noise, the click spring being preferably biased against a lever which is in operational contact with the pressure responsive means and adapted to actuate the click spring for supplying its click noise.
The present invention deals with the object of providing a less expensive and at the same time more reliable load monitoring test device for a patient""s foot of the kind as above referred. The test device when being used should moreover be adapted for securing a therapy as effective as possible by strictly complying with a series of multiple steps as prescribed by the patient""s physician subsequent to an operation for again obtaining a healthy leg or hip portion which has undergone an orthopedic operation.
A test device for monitoring a predetermined pressure load comprises in accordance with the present invention a pressure sensor which is to be placed under the heel to the patient""s foot for monitoring a predetermined pressure load. In accordance with a specific aspect under the present invention this pressure sensor is a circular, ring-shaped, curved washer which has a snap portion that is adapted for being snapped-over from a rest position under a predetermined pressure load and snapped into an active monitoring position whereby this snapping action is accompanied by an audible signal and further by a sensitive sensing signal acting bodily against the heel of the patient""s foot. Upon relief of the predetermined pressure load the snap portion of the curved washer will again be returned into its rest position. In accordance with a preferred embodiment of the test device according to the present invention the snap portion of the curved washer comprises a conically shaped elevation which surrounds the central opening of the curved washer and which is adapted to snap a respectively adjacent portion of the washer into its active monitoring position.
In accordance with a further preferred aspect of the present invention the circular, ring-shaped, curved washer is arranged between first and second pressure plates are designed as shoe inserts whereby a first pressure plate is used as a heel support for the patient""s foot and is preferably provided with an elevated portion which is in contact with the snap portion of the curved washer. The first and second pressure plates should both be designed as dishes in the form of a rest for the patient""s heel and should preferably be interlinked by a common pivot means for being relatively movable with respect to each other to thereby easily allow the arrangement of the curved washer between the two plates as well as its replacement against a new washer that will secure a monitoring of a different predetermined pressure load on the patiant""s foot.
A test device in accordance with the present invention is accordingly most distinguished over comparable devices of the prior art in the feature of providing not only an audible signal when a predetermined pressure load is reached but in providing also a sensitive sensing signal that bodily acts against the heel of the patient""s foot. Such a sensitive sensing signal will definitely be felt even by elder people for then immediately reacting with a relief of the pressure load on the foot of the leg that is under recovery. The test device may also be produced at low costs and may be maintained safely over a long period due to its absence of separate fluid or other signal lines.